Tree decay detection with the Picus Sonic Tomograph 

The Picus uses the fact that the velocity of sound in wood depends on the modulus of elasticity and the density of the measured wood. Most types of damage which impair safety by increasing the likelihood of fracture - in particular cavities, white rots and brown rots - reduce elasticity and density in the wood.

Problem with former sonic assessments

These wood characteristics (density and elasticity) vary both within a tree species and between tree species. Comparing individual sound velocities, measured on a specific tree, using tabulated values, only detects extensive damage.

Relation of the colours to the sound velocities

The colours shown on the tomogram are determined at the point at which two paths intersect. Areas with no intersection paths are classified according to the nearest confirmed intersection. 


Green areas, although of lower density in comparison to the brown areas, may not necessarily be decayed. Included bark etc may also show green, as well as the areas of degraded wood around more extensive zones of decay which show as purple or blue.